The impact of mancozeb on entomofauna communities in apple orchards

Two Large scale field studies have been conducted to the same design in commercial apple orchards in north and south France. Mancozeb (Dithane M-45) was applied at its post-annex I use rate of 1.6 kg a.i./ha on four occasions with a spray interval of 7 days. Reference treatments of a water treated control and toxic reference of dimethoate were also included. Studies were of randomized block design with 4 replicates (4 plots of 6 adjacent rows of 8 trees, on a surface of approximately 16 x 21 m) per treatment. Leaf and canopy dwelling arthropods were sampled before and at regular intervals after application until the end of the season. A diverse range of arthropod taxa was sampled, counted and identified which enabled for an evaluation of key taxa such as predatory mites and other beneficials but also of the whole foliar dwelling arthropod community. This two level analysis allows for a thorough investigation of both direct and indirect effects of the test item on beneficial, pest and non-target arthropods and for a state of the art evaluation at the ecological community Level using ordination techniques. The findings from the two locations were highly consistent in that mancozeb applied four times at 1.6 g a.i./ha with a 7 day spray interval caused significant but short lived reductions in predatory Phytoseiid mites of >50% with rapid recovery approximately one month after application. These transient effects did not impact secondary pests such as rust mites (Eriophyoidea) and broad mites (Tarsonemidae). A wide range of arthropod taxa were investigated (229 taxa in the north and 215 taxa in the south) and consistent adverse treatment related effects were not noted for any taxa other than Phytoseiidae. At a lower rate of mancozeb representing potential off-field deposits at 3 m due to drift effects were virtually absent on predatory mites in and to all other taxa present.